JP6193794B2 - Method for forming a rectangular battery case - Google Patents

Description

  The present invention relates to a method for forming a rectangular battery case which is a case of a Li-ion battery or the like.

  Lithium ion secondary batteries (Li ion batteries) are widely used as power sources for mobile phones, notebook personal computers, electric vehicles, hybrid vehicles, and the like. In many cases, a metal including a lid is used for a plate material constituting this Li ion battery case (hereinafter also simply referred to as a battery case), and an iron alloy such as stainless steel or an aluminum alloy is used. . In particular, it is advantageous in terms of corrosion resistance, weight reduction, workability, and cost when the battery case lid, the body (can), and the like are made of a molded product obtained by press-molding an aluminum alloy plate (cold rolled plate) material.

  As the shape of these battery cases, as a battery case with a high mounting efficiency and excellent heat dissipation performance and a square cross-sectional shape, the flatness, that is, the ratio of the width of the wide surface to the width of the narrow surface Large, flat battery cases (where the short side is significantly smaller than the long side) are widely used. Such a rectangular battery using a thin rectangular battery case is regarded as important because it is suitable for reducing the thickness and weight of the device and has a high space effect.

  As a method for forming such a square battery case (battery can) with a high flatness, as a transfer drawing method, a metal plate such as an aluminum alloy is used as a forming material, and deep drawing and ironing using a transfer press machine. It has been performed to obtain a molded shape by repeating the processing for 10 to 20 steps (stages). However, in such a molding method, a large number of expensive dies are required because of the multi-step process, the equipment cost is increased by a large transfer press, and the processing by the large press cannot increase the press speed. There were problems such as low productivity.

  For this reason, conventionally, various proposals have been made in order to solve the problems related to the formation of the rectangular battery case as described above.

  For example, in Patent Document 1, as a battery can material punched into a predetermined shape, a cold-rolled steel sheet containing 0.1% or less of carbon is deep-drawn to obtain a first rectangular tube having a substantially elliptical cross-sectional shape. After forming, the square battery case is formed by DI processing that continuously performs drawing and ironing at once.

  However, in the method using the DI molding method that continuously performs drawing and ironing such as Patent Document 1, an aluminum alloy plate is secured to a square battery case with high flatness, and the plate thickness and shape accuracy are secured. Molding with is difficult. This is because an aluminum alloy plate having a characteristic that is soft and has a low elastic modulus with respect to an iron alloy or steel such as SUS having a high rigidity is greatly different in behavior and characteristics at the time of forming.

  On the other hand, in Patent Document 2 and Non-Patent Document 1, a taper is provided on the upper edge of the container by the first drawing (initial drawing), or a spare bottom surface portion having an outer diameter smaller than the product bottom surface portion, It is disclosed that an intermediate (preliminary) molded body is obtained by forming a pre-inclined side wall portion inclined from a bottom surface portion. By redrawing this, the bend angle by the die face of the side wall portion of the intermediate molded body is made smaller than 90 degrees due to the presence of the taper and the pre-inclined side wall portion, and resistance to the flow of materials such as friction. It has been proposed to carry out redrawing while reducing the size.

Japanese Patent No. 4119612 Japanese Patent No. 4325515

Plastic Processing 2, W. Johnson, P.B. Co-authored by Meller, published on October 30, 1965, Baifukan, "11.10 Redrawing of bottomed containers" pages 26-27

  However, even when the forming method of Patent Document 2 or Non-Patent Document 1 is used, the aluminum alloy plate is formed into a square battery case with high flatness by the DI forming method in which drawing and ironing are continuously performed. It is still difficult to ensure thickness and shape accuracy.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a forming method capable of forming an aluminum alloy plate into a rectangular battery case with high flatness with high accuracy and efficiency. .

In order to achieve the above object, the gist of the method for forming a rectangular battery case of the present invention is as follows:
A raw aluminum alloy plate is drawn to form a bottom portion and a side wall portion that rises from the periphery of the bottom portion, and an inclined wall surface that is reduced in diameter toward the bottom portion is partially formed around the four sides of the side wall portion. A first drawing step for forming the first rectangular tube;
The first rectangular tube body is redrawn to have a bottom portion and a side wall portion rising from the periphery of the bottom portion, and a slanted wall surface whose diameter is reduced toward the bottom portion is a portion extending around the four sides of the side wall portion. A second rectangular tube that is formed in a second shape and has a height of the side wall portion higher than that of the first rectangular tube, and further leaves the bottom of the first rectangular tube as the bottom. A second drawing process to be molded;
The second square tube body is processed to have a bottom portion and a side wall portion rising from the periphery of the bottom portion, and the side wall portion has a height higher than that of the second square tube body, and the side wall portion. The plate thickness is 60% or less of the thickness of the aluminum alloy plate, and further comprises a finishing step of forming into a rectangular battery case, leaving the bottom of the second rectangular tube as the bottom,
That is.

  In the first drawing process, the present invention forms a first rectangular tube in which a slanted wall surface that is reduced in diameter toward the bottom is partially formed around the four sides of the side wall. Due to the existence of the inclined wall surface, the bending angle of the side wall portion of the first rectangular tube to be molded is made smaller than 90 degrees when the first rectangular tube is redrawn by the second drawing step. .

  Thereby, when the first rectangular tube is redrawn, deformation resistance due to bending of the side wall portion is reduced. As a result, the drawing in the second step is performed more smoothly and the formability is improved, so that a thin material metal plate can be formed into a bottomed rectangular battery case with high flatness.

  In addition to this, by performing the second drawing and finishing so that the bottom of the first rectangular cylinder remains as the bottom of the rectangular battery case, the first and second rectangular cylinders are obtained. Except for each bottom portion, side wall portions including the inclined wall surfaces of the first and second rectangular tube bodies are mainly molded. For this reason, compared with the case where each bottom part and side wall part of a 1st, 2nd square cylinder body are shape | molded together, the deformation resistance by bending is reduced more.

  By combining these slanted wall surface formation and the bottom of the first rectangular tube as it is as the bottom of the rectangular battery case, its height is higher than that of the second rectangular tube, and the final thickness of the side wall is reduced. An aluminum alloy prismatic battery case reduced to 60% or less of the thickness of the material aluminum alloy plate can be molded with high accuracy and with a small number of steps.

It is sectional drawing of a press apparatus which shows the one aspect | mode of the 1st drawing process of this invention. It is sectional drawing of a press apparatus which shows the one aspect | mode of the 2nd drawing process of this invention. It is sectional drawing of a press apparatus which shows the one aspect | mode of the finishing process of this invention. It is a perspective view which shows the raw material blank 1 shape | molded by FIG. It is a perspective view which shows the 1st square cylinder 2 shape | molded by FIG. It is a perspective view which shows the 2nd square cylinder 3 shape | molded by FIG. FIG. 4 is a perspective view showing a final rectangular battery case 4 molded in FIG. 3.

  Hereinafter, a preferred embodiment of the present invention in which a material aluminum alloy plate is formed into a rectangular battery case will be described in detail with reference to the drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the present invention, after the first drawing process in FIG. 1 and the second drawing process (redrawing process) in FIG. 2, the product shown in FIG. 7 is obtained by the third finishing process in FIG. Mold a square battery case. The finishing process of FIG. 3 shows an example of the ironing process, and shows an aspect of forming the product prismatic battery case shown in FIG. 7 by combining with the drawing process of FIGS. Here, the first, second, and third designations of the steps in the present invention merely indicate the order and distinction of the steps, and the steps are limited to only the first, second, and third. It does not mean that no other process enters between the first, second and third processes. That is, it is included in the scope to add other steps such as molding and surface treatment as appropriate between the first, second, and third steps and between the first, second, and third steps.

First Drawing Process In the first drawing process shown in FIG. 1, a material aluminum alloy plate 1 as shown in FIG. 4 is replaced with a first square punch (punch) 10 as shown in FIG. And drawing with a square die (die) 11. Then, it is formed into a first rectangular tube 2 that is square in a plan view as shown in FIG.

  For this reason, first, a material aluminum alloy plate (material blank) 1 punched in advance in a predetermined shape such as a circle, a rectangle, or an ellipse (a mode shown in FIG. 4) in a plan view is mounted on the press apparatus shown in FIG. .

  Then, the blank holder 12 and the first die 11 sandwich and hold the peripheral portion 1b of the material aluminum alloy plate 1, and then the first square punch 10 is lowered or the first square die 11 is raised. The raw aluminum alloy plate 1 is drawn into a rectangular first rectangular tube 2 shown in FIG. 5 in cooperation with the first punch 10 and the first die 11.

  Here, the first punch 10 and the first rectangular die 11 in FIG. 1 are square shapes corresponding to or similar to the first rectangular cylindrical body 2 in the same plan view as shown in FIG. Rectangular cross-sectional shape). In addition, the first square punch 10 has a slant wall surface (taper surface) 10a which is reduced in diameter toward the tip 10b side, and is partially formed around the four circumferences.

  As a result, as shown in the cross-sectional view of FIG. 1 or the perspective view of FIG. 5, the bottom portion 2d has a square shape in plan view, and four side wall portions 2a, 2a, 2b, 2b rising from the periphery of the bottom portion 2d. First slanted cylindrical body in which four slanted wall surfaces 2f, 2f, 2g, and 2g that reduce in diameter toward the bottom portion 2d are partially formed around the four sides of the side wall portions 2a, 2a, 2b, and 2b. 2 is molded. In the first rectangular tube 2 of FIG. 5, 2a and 2a are two opposing side wall portions on the large and wide long side, and 2b and 2b are two opposing side wall portions on the narrow short side. 2c is an opening above the hollow part, 2d is a bottom part, and 2e is a flat product outer flange that spreads outward from the peripheral part of each side wall 2a, 2b.

(Slanted wall)
As described above, the first square punch 10 is partially formed with an inclined wall surface (tapered surface) 10a that is reduced in diameter so as to decrease in diameter toward the tip 10b. . With the inclined wall surface 10a, the inclined wall surfaces (inclined walls) 2f and 2f are formed on the two wide side walls 2a and 2a on the wide long side of the first rectangular tube 2, respectively, and as shown in FIG. The oblique wall surfaces 2g and 2g are formed on the two side wall portions 2b and 2b on the narrow short side, respectively.

  As a result, the first rectangular tube 2 has four sides (full length or two) of each side wall 2a, 2a, 2b, 2b between the bottom 2d and each of the four side walls 2a, 2a, 2b, 2b. Oblique wall surfaces 2f, 2f, 2g, and 2g are formed over the entire width. Here, the inclined wall surfaces 2f and 2f exist respectively over the widths (lengths) of the two wide side walls 2a and 2a, and the inclined wall surfaces 2g and 2g are two narrow side edges. Each exists over the width (length) of the side walls 2b, 2b.

  These inclined wall surfaces 2f, 2f, 2g, and 2g have a substantially rectangular cross section formed by the side wall portions 2a, 2a, 2b, and 2b from the side wall portions 2a, 2a, 2b, and 2b toward the bottom portion 2d. The long side and the short side are sequentially narrowed, and the inclined wall surfaces 2f, 2f and 2g, 2g are wall surfaces that are inclined so that the distance between the long side and the short side becomes the long side and the short side sequentially.

  The inclined wall surfaces 2f, 2f, 2g, and 2g are formed on the inclined wall surfaces 2f, 2f, 2g, and 2g of the first rectangular tube body 2 when formed in the second drawing process described later in FIG. Each bending angle is provided to make it smaller than 90 degrees. With the inclined wall surfaces 2f, 2f, 2g, 2g, when the first rectangular tube body 2 is redrawn (formed) as shown in FIG. 2, the inclined wall surface 3f of the second rectangular tube body 2, Each bending angle R (R shown in FIG. 2) of 3f, 3g, and 3g can be made smaller than 90 degrees. For this reason, the deformation resistance due to bending of the side wall portions 3a, 3a, 3b, 3b including the inclined wall surfaces 3f, 3f, 3g, 3g of the second rectangular tube body is reduced. As a result, the redrawing process is performed more smoothly and the formability is improved, so that a thin metal sheet can be formed into a bottomed rectangular battery case with high flatness. Here, the bending angles R of the inclined wall surfaces 3f, 3f, 3g, and 3g of the second rectangular tube 2 are angles R formed by the side walls 3f, 3f, 3g, and 3g, as shown in FIG. It is.

  In the first rectangular tube 2, the shape conditions such as the inclination or height of the inclined wall surfaces 2 f, 2 f, 2 g, and 2 g are the same as those of the first face when formed by the die face in the second step. It is determined from the design conditions that can make each bending angle of the inclined wall surfaces 2f, 2f, 2g, and 2g of the rectangular cylinder 2 smaller than 90 degrees.

  In the first drawing step, the thickness is the same as or increased from the original material aluminum alloy plate 1, the cross-sectional shape is rectangular, and the first has a certain height (depth). Molded as a rectangular tube 2.

(First square tube bottom)
The size (width and length) of the bottom 2d of the first rectangular tube 2 is such that the long side and the short side of the bottom 2d are the first corners in order to provide the inclined wall surfaces 2f, 2f, 2g, and 2g. The long side and the short side of the cylindrical body 2 are smaller than each other, and the area of the cross section of the bottom 2d is smaller than that of the first rectangular cylindrical body 2.

  On the premise of this, in the present invention, the bottom 2d of the first rectangular tube 2 formed in the drawing step of the first step is replaced with the bottom 4d of the final rectangular battery case 4 shown in FIG. Or left as the bottom 4d.

  For this purpose, the bottom portion 2d is formed to be the same as or slightly larger than the bottom portion 4d so as to have a size and shape corresponding to the bottom portion 4d of the prismatic battery case 4 as a product. Further, a bottom 2d of the first rectangular tube 2 is left as it is or left as much as possible so that it remains as a bottom 3d of the second rectangular tube 3 and a bottom 4d of the rectangular battery case 4 as described later. 2. Drawing and finishing are performed.

  Here, the bottom 2d of the first rectangular tube body 2 is left as it is or is left as much as possible to become the bottom 4d of the final rectangular battery case 4. This bottom 2d itself can be obtained by redrawing or finishing. It remains substantially unmolded, and becomes the bottom 3d of the second rectangular tube 3 and the bottom 4d of the rectangular battery case 4 which are the same as the bottom 2d or of a certain size or more and have the same shape. Means. However, it is allowed that the size and shape of the bottom portion 2d slightly change in part or in the periphery of the bottom portion when the bottom portion 2d is subjected to some molding in the redrawing processing and finishing processing. Here, as a guideline for making the bottom part 4d of the rectangular battery case 4 as it is or leaving the bottom part 2d of the first rectangular tube body 2 as it is, the area of the bottom part of the rectangular battery case 4 of FIG. (Side × short side) is set in a range of 70 to 100% of the area (long side × short side) of the bottom 2d of the first rectangular tube 2 in FIG.

  In Patent Document 2 and Non-Patent Document 1, a taper is provided on the upper edge of the container by the first drawing (initial drawing), or a preliminary bottom surface portion having an outer diameter smaller than the product bottom surface portion, and an inclination from the preliminary bottom surface portion. An intermediate (preliminary) molded body is obtained by forming a preliminarily inclined side wall portion. However, the bottom portion of the intermediate (preliminary) molded body does not remain as the bottom portion of the product shape as in the present invention, and is molded together with the side wall. In other words, the area (long side × short side) of the bottom of the rectangular battery case 4 of FIG. 7 is inevitably less than 70% of the area (long side × short side) of the bottom 2d of the first rectangular tube 2. It becomes smaller (Non-patent document 1) or conversely exceeds 100% and inevitably becomes larger (Patent document 2). For this reason, the resistance to the flow of the material at the time of molding becomes larger as compared with the present invention in which the bottom part is formed as a bottom part and the side wall is formed as a side wall in order.

  In the case of the present invention, the shape of the first rectangular tube 2 after the first drawing is composed of a bottom 2d and inclined wall surfaces 2f, 2f, 2g, 2g, as shown in FIGS. A convex surface is formed on the bottom 2d side of the first rectangular tube 2. As a result, the material on the bottom 2d side is subjected to bulge forming during the first drawing, and thinning occurs. For this reason, also in the finally obtained rectangular battery case shown in FIG. 7, the thickness of the bottom portion is reduced and the material flows toward the side wall, so that the shape of the deep rectangular battery case can be obtained with less material usage. It is done. Accordingly, an effect of reducing the amount of material used for the battery can can be obtained. Further, in the case of the present invention, since the bending angle at the die shoulder is small in the redrawing process described later, bending deformation that occurs in the vertical wall portion of the finally obtained rectangular battery case (battery can) shown in FIG. As a result, the surface unevenness caused by the battery is reduced, and a battery case with higher strength can be obtained.

  The first drawing process may be performed in one stage, a plurality of stages, or multiple stages, and a normal press apparatus can be used. In the drawing, the forming speed can be set in the range of 1 to 60 m / SPM, and the wrinkle pressing load can be set in the range of 0.5 to 500 kN in a normal press apparatus or drawing. In addition to the first drawing process, the second drawing process and the finishing process use various commercially available lubricants or lubricating oils as necessary, as in the case of a normal press or drawing process. it can.

Second Drawing Process Next, in the redrawing process, which is the second drawing process of FIG. 2, the molded first rectangular tube 2 shown in FIG. The second rectangular punch 13 and the second rectangular die 14 are used to redraw the second rectangular cylinder 3 having a rectangular cross section. That is, the second rectangular cylinder 3 shown in FIG. 5 is formed by the second rectangular punch 13 and the second rectangular die 14 in which the inclined wall surface that is reduced in diameter toward the tip side is partially formed over the four circumferences. To redraw.

  Here, the second punch 13 and the second square die 14 in FIG. 2 are square shapes corresponding to or similar to the second rectangular cylinder 3 having a square shape in plan view as shown in FIG. Rectangular cross-sectional shape). Further, as in the square punch 10 of FIG. 1, the second square punch 13 is partially formed with an inclined wall surface (taper surface) 13a that is reduced in diameter toward the tip 13b side, around the four circumferences. doing. In addition, the second square die 14 is partially formed with an inclined surface (tapered surface) 14a whose diameter decreases toward the lower side of the second square die 14 around the periphery thereof.

  By means of the inclined wall surface 13a, the side wall portions 2a, 2a including the inclined wall surfaces (inclined walls) 2f, 2f of the first rectangular tube body 2 are connected to the wide long side of the second rectangular tube body 2. Two side wall portions 3a and 3a and inclined wall surfaces (inclined walls) 3f and 3f are formed. Further, the side wall portions 2b and 2b including the inclined wall surfaces (inclined walls) 2g and 2g of the first square tube body 2 are formed as two side wall portions on the narrow short side of the second square tube body 3. 3b and 3b, and inclined wall surfaces (inclined walls) 3g and 3g, respectively.

  As a result, the slant wall surface 3f, 3f, 3g, 3g, which is composed of the bottom portion 3d and the side wall portions 3a, 3a, 3b, 3b rising from the periphery of the bottom portion 3d as shown in FIG. Is partially formed over the four circumferences of the side wall portion, and the height of the side wall portions 3a, 3a, 3b, 3b is higher than that of the first square tube body 2, and the bottom of the first square tube body The 2nd square cylinder 3 which left 2d as the bottom 3d can be fabricated.

  When the first rectangular tube 2 is redrawn, the rectangular punch 13 has a cross-sectional shape similar to that of the first rectangular tube, such as the inclined wall surface 13a at the tip. The inclined wall surface 13a at the tip of 13 and the inclined wall surfaces 2f, 2f, 2g, 2g of the first rectangular tube body are matched and matched. As a result, the bending angles R of the side wall portions 2a, 2a, 2b, and 2b and the inclined wall surfaces 2f, 2f, 2g, and 2g of the first rectangular tube body 2 when molded can be made smaller than 90 degrees. Here, the bending angle R is R shown in FIG. 2, and the two side wall portions 3 a on the wide long side of the tapered rectangular portion 3 formed on the die 14 or the formed second rectangular tube body 3, This is the angle formed by 3a and the vertical direction.

  Further, as described above, the bottom 2d of the first rectangular tube 2 formed in the drawing step of the first step is left as it is or left as much as possible, and the final rectangular battery case 4 shown in FIG. Let it be the bottom 4d. That is, the first corner 2 is formed so that the bottom 2d of the first rectangular tube 2 is the same as or slightly larger than the bottom 4d so as to have a size and shape corresponding to the bottom 4d of the final rectangular battery case 4. The cylindrical body 2 is formed. That is, the area (long side × short side) of the bottom portion 4d of the rectangular battery case 4 of FIG. 7 is 70 to 100% of the area (long side × short side) of the bottom portion 2d of the first rectangular tube body 2 of FIG. Molding to be in the range.

  As a result, the bottom 2d of the first rectangular tube 2 is used as the bottom 3d of the second rectangular tube 3, and the side walls 2a, 2a, 2b, 2b and the inclined wall surfaces 2f, 2f of the first rectangular tube 2. 2g and 2g are sequentially formed as the side walls 3a, 3a, 3b, 3b and the inclined wall surfaces 3f, 3f, 3g, 3g of the second rectangular cylinder 3, so that the resistance to the flow of the material at the time of molding Becomes smaller. The same effect can be obtained in the finishing process described later.

  In the redrawing process of FIG. 2, more specifically, as shown in FIG. 2, the first rectangular tube 2 formed by the first drawing process of FIG. 1 is mounted on the press device. At this time, as shown in FIG. 2, the sleeve 15 is preferably inserted into a space (gap) 18 between the first rectangular tube body and the second rectangular punch 13. This is because a sleeve 15 is mounted in advance on the outer peripheral side (outer surface side) of the second square punch 13, and the sleeve 15 is mounted together with the second square punch 13 on the inner wall surface of the first square cylindrical body 2. Insert by lowering (or raising the second die 14) along 2a.

  The sleeve 15 has an inner size and a cross-sectional shape corresponding to the outer size and the cross-sectional shape of the second square punch 13, and the inner side of the first rectangular tube body 2 formed in the second redrawing process. In FIG. 2, the space (gap) that cannot be supported by the second square punch is filled.

  Then, as shown in FIG. 2, the second square punch 13 is lowered or the second square die 14 is raised, and only the second square punch 13 is advanced (entered) into the second square die 14. In addition, the second square punch 13 and the second square die 14 cooperate with each other to perform further redrawing through the sleeve 15. And it shape | molds in the 2nd square cylinder 3 shown in FIG.

  The second rectangular tube 3 has a smaller ratio of short side / long side (more flat) than the cross-sectional shape of the first rectangular tube 2, and the height of the first rectangular tube 2. It has a rectangular cross-sectional shape whose height h2 is higher than h1 over the height direction. In the drawing process shown in FIG. 2, the product outer flange 3e extending outward as shown in FIG. 6 is left, but the second rectangular tube body is left without leaving such a product outer flange 3e. 3 may be drawn.

  2 and 6, 3 a and 3 a are two large side walls facing each other on the long side, 3 b and 3 b are two side walls facing each other on the short side of the small and narrow side, 3c is an opening above the hollow portion, 3d is a bottom portion, and 3e is a flat product outer flange that spreads outward from the peripheral edge of each side wall 3a, 3b.

  In the example of FIG. 2, in the shape of the die 14 at the time of redraw molding, the upper surface 15 of the second square die 14 is set to the outer surface of the first rectangular tube 2 before redraw molding, particularly the inclined wall surface 2f. 2f, 2g, and 2g. As a result, the material that flows during redraw molding moves along the upper surface 15, so that wrinkles are not generated and smoother deformation occurs, and the moldability is further improved.

(Use of sleeve)
In the present invention, it is preferable to use a sleeve 15 fitted to the second punch 13 in the second drawing process. In the second drawing step, when the first rectangular tube 2 is redrawn to form a taller (deeper) second rectangular tube 3 having a smaller rectangular cross section. Of course, the second punch 13 has a rectangular cross-sectional shape smaller than that of the first rectangular tube 2. As a result, as shown in FIG. 2, a space (gap) that cannot be supported by the second punch 13 inevitably exists around the rectangular tube body 2.

  In the redrawing process without using a sleeve, when a molding force is applied from the mold 14 around the first rectangular tube 2 due to the presence of a space that is not supported by the second punch 13, this molding is performed. The load part of force is buckled and wrinkles are likely to occur. For this reason, there is a possibility that the thickness and shape accuracy cannot be ensured even if the molding cannot be performed due to uneven processing depending on the part. On the other hand, when the second rectangular tube 3 having a smaller diameter and a taller (deeper) cross-sectional shape is rectangular from the first rectangular tube 2 having a rectangular cross-sectional shape, the sleeve is formed. By using 15, the space can be filled. For this reason, even if a molding force is applied from a die (mold) 14 around the first rectangular tube 2, a load portion of the molding force in the first rectangular tube 2 is not buckled. I don't have a self For this reason, it can be formed as a uniform process regardless of the part, and plate thickness and shape accuracy can be secured.

  Naturally, the sleeve 15 filling the space (gap) having such a rectangular cross-sectional shape needs to have an angular annular cross-sectional shape that approximates or resembles the space (gap) 18. During the second redrawing process, the sleeve 15 is stopped at the initial insertion position of the molding, and only the second punch 13 is advanced into the second die 14 for molding. Try to go forward. Depending on the type of aluminum alloy to be molded, the material of the sleeve can be appropriately selected from the steel material for the mold, the same type of aluminum alloy, or the material of rubber or resin.

  Similarly to the first drawing process, the second drawing process may be performed in one stage, a plurality of stages, or multiple stages, and a normal press apparatus can be used. And the conditions in the drawing process are also the conditions of the first drawing process from the range in the normal press apparatus or drawing, such as the forming speed: 1-60 pieces / min, the wrinkle holding load: 0.5-500 kN. Can be set in relation to

Third finishing process:
After the multi-stage or multi-stage drawing as described above, the second rectangular tube 3 is further processed by drawing or ironing as a third process, or by drawing and ironing. The rectangular battery shown in FIG. 7 has a height higher than that of the second rectangular tube 3 and the final plate thickness of the side wall portion is reduced to at least 60% or less of the plate thickness of the aluminum alloy plate. Case 4 is molded.

  FIG. 3 shows a second square tube 3 having a rectangular cross-sectional shape by a ironing process as a finishing process, a third square punch 16 and a third square ironing die (die row) 17. In particular, the side wall 3a is ironed and thinned (thinned) to form the final rectangular battery case 4 shown in FIG. Here, the third square punch 16 and the third square ironing die 17 in FIG. 3 are square shapes corresponding to or similar to the rectangular battery case 4 in plan view, which are also square in plan view as shown in FIG. (Rectangular cross-sectional shape). As for the ironing process, the side wall thickness may be reduced stepwise by repeatedly performing a plurality of processes.

  During the ironing process, the inclined wall surfaces 3f, 3f, 3g, and 3g of the second rectangular cylinder 3 are all formed into the side walls 4a, 4a, 4b, and 4b of the rectangular battery case 4.

  In addition, the bottom 3d of the second rectangular tube 3 formed in the redrawing process has an area (long side × short side) of the bottom 4d of the rectangular battery case 4 so that the bottom 2d of the first rectangular tube 2 has the same area. The bottom part 4d of the rectangular battery case 4 is left as it is or left as much as possible so as to be in the range of 70 to 100% of the area (long side × short side). As a result, the bottom 3d of the second rectangular tube 2 serves as the bottom 4d of the rectangular battery case 4, and the side walls 3a, 3a, 3b, 3b and the inclined wall surfaces 3f, 3f, 3g, Since 3g is sequentially molded as the side walls 4a, 4a, 4b, and 4b of the rectangular battery case 4, the resistance to the flow of the material during molding becomes smaller.

  The final rectangular battery case 4 has a short side / long side ratio substantially the same as that of the rectangular cross-sectional shape of the second rectangular tube 3, and the second rectangular tube 3 (height h2). ), The height h3 is higher or deeper, and has a rectangular final cross-sectional shape. And by ironing, at least the final plate thickness of the side wall is reduced to 60% or less of the plate thickness of the material metal plate. In the final rectangular battery case 4 of FIG. 7, 4a is a large and wide two side walls facing each other on the long side, 4b is a small two narrow side walls facing each other on the short side, and 4c is an opening above the hollow part. 4d is the bottom. Even at the stage of the rectangular battery case 4 in FIG. 7, the product outer flange 4e that spreads outward is left. However, the square battery case 4 may be finished without leaving such a product outer flange 4e. good. Such a product outer flange 4e is removed by a trimming process.

  In the present invention, after the drawing shown in FIGS. 1 and 2 is repeated to form the second rectangular tube body 3 having a square cross-sectional shape, the above-described sleeve is not used in the ironing process of FIG. The final rectangular battery case 4 is formed by ironing to reduce only the plate thickness (wall thickness) without changing the thickness. For this reason, there is no occurrence of molding defects such as wrinkles as in the conventional combined processing with drawing and ironing, and stable molding with excellent shape and thickness accuracy is possible.

  The ironing process, which is the finishing process, can use not only one stage as shown in FIG. 3 but also a press device, conditions, and lubricating oil that perform multi-stage ironing.

Square battery case:
The final rectangular battery case 4 shown in FIG. 7 has a rectangular flat thin cross-sectional shape in which the ratio of the short side / long side is substantially the same as the rectangular cross-sectional shape of the second rectangular tube 3. And it is a box shape (box body) shape whose height h3 (height or deep) is higher than the second square cylinder body 3 (height h2). Further, the plate thickness (wall thickness) is a thin wall thickness obtained by reducing the final plate thickness of the two side walls 4a and 4b subjected to the ironing process to 60% or less of the plate thickness of the material metal plate.

  The final plate thickness of the side wall 3a depends on the length (width) and height h3 of the long side wall 4a, the short diameter side wall 4c, the short side / long side ratio, and the required characteristics from the usage of the rectangular battery case 4. , Etc. In this regard, according to the specifications of a normal Li ion secondary battery or the like, the plate thickness of the side wall 4a of the rectangular battery case 4 is selected from a range of 0.3 to 2 mm. If the thickness of the side wall 4a is less than 0.3 mm, the required rigidity and strength may be insufficient depending on the strength of the material metal plate. On the other hand, if the thickness of the side wall 4a exceeds 2 mm, the weight becomes heavy, and it becomes difficult to perform processing with high accuracy such as a thin-walled portion or a breaking groove for a safety valve. The final thickness of the bottom 4d may be the same as the material metal plate shown in FIG. 1 depending on the required characteristics from the usage of the rectangular battery case 4, or may be different from this, or different from this. You can make it thinner.

  Although not shown, this rectangular battery case 4 is provided with a sealing lid provided with other necessary parts such as an external positive electrode, an electrolyte inlet and a cover, and a safety valve, as a Li ion battery case. .

Material aluminum alloy plate:
When the material aluminum alloy plate used in the present invention is reduced to 60% or less of the thickness of the material plate by both drawing and ironing, the thickness of the side wall 4a is in the range of 0.3 to 2 mm. It shall have a plate thickness. The reduction in the thickness of the battery case 4 is directly linked to the increase in the internal volume and is an important factor for increasing the capacity of the battery characteristics. However, the battery case 4 can maintain the required pressure resistance even when the thickness is reduced. Both drawing and ironing must be possible. For this reason, the aluminum alloy sheet must be excellent in formability to a thin rectangular battery case when combined with drawing and ironing, and it must have excellent corrosion resistance and high strength and rigidity even if it is thin. is there. In view of these points and weight reduction, an aluminum alloy plate is preferable.

  The material strength of the material aluminum alloy plate is preferably in the range of 30 to 180 MPa, with 0.2% proof stress after tempering such as solution treatment and quenching treatment, age hardening treatment, cold rolling and annealing, if necessary. . As an aluminum alloy satisfying these requirements, 3000 (Al-Mn) aluminum alloy standardized by JIS or AA is preferable, and A3003 aluminum alloy is preferable, and 1000 series aluminum alloy standardized by JIS or AA is preferable. When used and sealed, A1050 alloy which is a pure aluminum alloy is preferable. These alloys are also preferable from the viewpoint of corrosion resistance. However, depending on the use conditions and the molding conditions, alloys in which the creep resistance (creep deformation resistance) of these alloys is further improved, or higher strength 5000 series or 6000 series aluminum alloys may be used.

  As mentioned above, this invention can provide the shaping | molding method which can shape | mold an aluminum alloy plate in a square battery case with high flatness accurately and efficiently. For this reason, it can use suitably for the manufacturing process of the square battery case for lithium ion secondary batteries.

1: Raw metal plate, 2: First square tube, 2a, 2b: Side wall, 2d: Bottom, 2f, 2g: Oblique wall surface, 3: Second square tube, 2a, 2b: Side wall, 3d: Bottom 3f, 3g: oblique wall surface, 4: square battery case, 4a, 4b: side wall, 4d: bottom, 10: first square punch, 11: first square die, 12: blank holder, 13: second Square punch, 14: second square die, 15: sleeve, 16: third square punch, 17: third square ironing die

Claims (3)

A raw aluminum alloy plate is drawn to form a bottom portion and a side wall portion that rises from the periphery of the bottom portion, and an inclined wall surface that is reduced in diameter toward the bottom portion is partially formed around the four sides of the side wall portion. A first drawing step for forming the first rectangular tube;
The first rectangular tube body is redrawn to have a bottom portion and a side wall portion rising from the periphery of the bottom portion, and a slanted wall surface whose diameter is reduced toward the bottom portion is a portion extending around the four sides of the side wall portion. A second rectangular tube that is formed in a second shape and has a height of the side wall portion higher than that of the first rectangular tube, and further leaves the bottom of the first rectangular tube as the bottom. A second drawing process to be molded;
The second square tube body is processed to have a bottom portion and a side wall portion rising from the periphery of the bottom portion, and the side wall portion has a height higher than that of the second square tube body, and the side wall portion. The plate thickness is 60% or less of the thickness of the aluminum alloy plate, and further comprises a finishing step of forming into a rectangular battery case, leaving the bottom of the second rectangular tube as the bottom,
A method for forming a rectangular battery case. In the first drawing step, the material aluminum alloy sheet is formed by a first square punch and a first square die, each of which has a slant wall surface that is reduced in diameter toward the tip side and is partially formed over four circumferences. The drawing process,
In the second drawing step, a second rectangular punch that partially forms an inclined wall surface that is reduced in diameter toward the tip side over the four circumferences, and the inclined wall surface of the second rectangular tube body Redrawing the first rectangular cylinder with a second square die having a corresponding inclined wall surface;
The finishing process is performed by ironing.
The method for forming a prismatic battery case according to claim 1.   3. The method for forming a rectangular battery case according to claim 1, wherein an area of a bottom portion of the rectangular battery case is in a range of 70 to 100% of an area of a bottom portion of the first rectangular tube body.

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